Portable tables, usually collapsible, are used for convenient transport between different locations and for preparing locales for periodic activities ranging from banquets to card games. Such tables must be lightweight for easy lifting and moving but must at the same time approach or equal the strength of conventional, heavy, non-portable tables. Those portable tables which are sturdy and able to handle heavy loads are often cumbersome, heavy, and inconvenient to move, while those which are lightweight and easy to transport are often weak and unstable.
These tables must be attractive enough for use in a wide range of settings, and must be extremely durable. Frequent moving of the tables exposes them to considerable knocking about in harsh circumstances, which the tables must be able to withstand with a minimum of noticeable damage. They must be able to maintain their integrity and shape through wide temperature differences during both use and storage.
Examples of prior art tables include Morgan et al., U.S. Pat. No. 2,717,187, which discloses a tabletop comprising a relatively thick wood core having top and bottom crossbands of suitable veneer and upper and lower plastic sheets bonded to the core. Morgan et al. teaches that the lower plastic sheet is necessary to the proper functioning of the tabletop to balance stresses induced by the upper plastic sheet. A further layer of material is provided under the lower plastic sheet. Goodman, U.S. Pat. No. 2,216,171, O'Conner, U.S. Pat. No. 1,934,372, Campbell, U.S. Pat. No. 2,251,395, and Wagner, U.S. Pat. No. 1,544,289, each disclose a tabletop comprising a panel made of stiff material, such as wood, loosely covered with a flexible nonresilient material such as fabric, paper, or leather for appearance and protection of the wood.
It has been found that plastic or polymer tabletops satisfy many requirements of portable tables. They tend to retain a satisfactory appearance after considerable wear and tear, and they resist marking. However, without reinforcement either through internal fibers or additional layers of support material, an amorphous and isotropic plastic normally lacks sufficient strength. Additionally, since a plastic top tends to warp easily due to heat, as for example when a hot food item is placed upon it, the conventional wisdom in the art has been that a plastic cover with a reinforcing layer bonded beneath it must be stiffened or balanced in some way. For example, we have seen that Morgan et al. uses a bottom layer of plastic bonded to a thick wood core to "balance" the stresses of the top plastic layer.
Plastic covers over reinforcing layers often experience delamination from the reinforcing layers at high temperatures, destroying the strength and integrity of the tabletop. This has been true especially where the adjacent reinforcing layer is constructed of a heat insulating material such as wood.